Total: Brazil Drilling No Risk to Amazon Reef

"Drilling activity will not impact the reef system," a spokeswoman for Total told the Thomson Reuters Foundation.

The company is working closely with Brazil's environmental enforcement agency (IBAMA) and needs their go ahead before it begins to drill, she said in an email.

It was not clear when a final ruling will be issued but Total says it expects to drill exploratory wells this year.

Total operates five blocks in the deep waters of the Foz do Amazonas Basin north of Brazil, which has already carried out a full environmental impact assessment, the company said.

But that was before discovery of the reef, according to the prosecutor in the state of Amapa on Brazil's Caribbean coast.

Oil companies "did not take into account the important ecosystem of the coral reef at the mouth of the Amazon River," Joaquim Cabral da Costa Neto, Brazil's federal prosecutor in Amapa state, said in a statement.

Scientists announced the discovery of the 600-mile reef system last year, a unique find because coral does not usually thrive in muddy waters like those of the Amazon.

With only about 5 percent of the system mapped, scientists do not know its scale and expect to discover new species of plants and animals living there, according to Nils Asp, a researcher at the Brazil's Federal University of Para.

"Exploration in an area close to corals, without adequate environmental impact studies can cause irreparable damage to this unique and little known biome," said Neto, the prosecutor.

The first photos of the reef system - which is up to 120 meters deep - were released earlier this year by the environmental campaign group Greenpeace.

They show bulbous purple and red coral formations and tropical fish swimming through waters stretching from northern Brazil to French Guyana.

"We brought up the most amazing and colourful animals I had ever seen on an expedition," Patricia Yager, a University of Georgia scientist, said last year when she and other researchers first announced the reef discovery in an academic journal.

All that is at risk should oil leak out, critics say.

The Amapa prosecutor said potential leaks "could cause damage to the marine... ecosystem environment not only in Brazil but also in neighbouring countries in the Caribbean region".

The area could contain as much as 14 billion barrels of oil, according to preliminary estimates from Brazil's government.

The British oil giant BP also has concessions in the area. The company did not respond to requests for comment.